我有一组复杂的优化选择，遭受物理读取。没有它们，它们会更快！
这些物理读取是由于WITH子句，每个WITH子查询一个physical_read_request。它们对我来说似乎完全没用，我更喜欢Oracle将子查询结果保存在内存中，而不是将它们写入磁盘并再次读取它们。
我正在寻找一种方法来摆脱这些物理读物。
具有相同问题的简单样本是：
编辑：示例替换为不使用字典视图的简单示例。
alter session set STATISTICS_LEVEL=ALL;
create table T as
select level NUM from dual
connect by level <= 1000;
with /*a2*/ TT as (
select NUM from T
where NUM between 100 and 110
)
select * from TT
union all
select * from TT
;
SELECT * FROM TABLE(dbms_xplan.display_cursor(
(select sql_id from v$sql
where sql_fulltext like 'with /*a2*/ TT%'
and sql_fulltext not like '%v$sql%'
and sql_fulltext not like 'explain%'),
NULL, format=>'allstats last'));
并且相应的执行计划是
SQL_ID bpqnhfdmxnqvp, child number 0
-------------------------------------
with /*a2*/ TT as ( select NUM from T where NUM between 100 and
110 ) select * from TT union all select * from TT
Plan hash value: 4255080040
---------------------------------------------------------------------------------------------------------------------------------------------------------------
| Id | Operation | Name | Starts | E-Rows | A-Rows | A-Time | Buffers | Reads | Writes | OMem | 1Mem | Used-Mem |
---------------------------------------------------------------------------------------------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 1 | | 22 |00:00:00.01 | 20 | 1 | 1 | | | |
| 1 | TEMP TABLE TRANSFORMATION | | 1 | | 22 |00:00:00.01 | 20 | 1 | 1 | | | |
| 2 | LOAD AS SELECT | | 1 | | 0 |00:00:00.01 | 8 | 0 | 1 | 266K| 266K| 266K (0)|
|* 3 | TABLE ACCESS FULL | T | 1 | 11 | 11 |00:00:00.01 | 4 | 0 | 0 | | | |
| 4 | UNION-ALL | | 1 | | 22 |00:00:00.01 | 9 | 1 | 0 | | | |
| 5 | VIEW | | 1 | 11 | 11 |00:00:00.01 | 6 | 1 | 0 | | | |
| 6 | TABLE ACCESS FULL | SYS_TEMP_0FD9D6646_63A776 | 1 | 11 | 11 |00:00:00.01 | 6 | 1 | 0 | | | |
| 7 | VIEW | | 1 | 11 | 11 |00:00:00.01 | 3 | 0 | 0 | | | |
| 8 | TABLE ACCESS FULL | SYS_TEMP_0FD9D6646_63A776 | 1 | 11 | 11 |00:00:00.01 | 3 | 0 | 0 | | | |
---------------------------------------------------------------------------------------------------------------------------------------------------------------
Predicate Information (identified by operation id):
---------------------------------------------------
3 - filter(("NUM">=100 AND "NUM"<=110))
Note
-----
- dynamic sampling used for this statement (level=2)
在每个WITH视图创建时看到（phys）Write，在第一个视图用法时看（phys）Read。我还尝试了RESULT_CACHE提示（这不反映在此示例选择中，但反映在我的原始查询中），但它也没有删除磁盘访问（这是可以理解的）。
如何摆脱物理写入/读取？